Mass-separated Ion Beam Research Articles

In-source and in-trap formation of molecular ions in the actinide mass range at CERN-ISOLDE

The use of radioactive molecules for fundamental physics research is a developing interdisciplinary field limited dominantly by their scarce availability. In this work, radioactive molecular ion beams containing actinide nuclei extracted from uranium carbide targets are produced via the Isotope Separation On-Line technique at the CERN-ISOLDE facility. Two methods of molecular beam production are studied: extraction of molecular ion beams from the ion source, and formation of molecular ions from the mass-separated ion beam in a gas-filled radio-frequency quadrupole ion trap. Ion currents of U+, UO1−3+, UC1−3+, UF1−4+, UF1,2O1,2+ are reported. Metastable tantalum and uranium fluoride molecular ions are identified. Formation of UO1−3+, U(OH)1−3+, UC1−3+, UF1,2O1,2+ from mass-separated beams of U+, UF1,2+ with residual gas is observed in the ion trap. The effect of trapping time on molecular formation is presented.

Progress towards the FRIB-EDM[formula omitted]-Frontend: A tool to provide radioactive molecules from isotope harvesting for fundamental symmetry studies

The under-construction FRIB-EDM3-instrument was designed to study polar radioactive molecules (such as RaF) in transparent cryogenic solids by laser spectroscopy. The instrument is divided into a frontend- and a backend section. The frontend accepts an aqueous sample from isotope harvesting and provides a mass-separated molecular ion beam in an ultra-high vacuum environment. In the backend, the ions are guided into alkali-metal vapor and the resulting neutrals are co-deposited in a solid argon matrix to perform laser spectroscopy. This work addresses the frontend of the instrument. The efficient ionization of harvested radioisotopes from aqueous samples is achieved with a spray-ionization method. Subsequently, the molecular ion beam is analyzed by mass-to-charge ratio by a quadrupole mass filter. To verify the feasibility of the approach, numerical simulations with the COMSOL and SIMION packages have been conducted. While the former was applied to study transport in ion funnels, the latter was used to investigate ion beam transmission through the lower pressure sections. Following promising simulation results, a first experimental setup is under construction.

Effect of Nitrogen Ion Implantation on the Tool Life Used in Particleboard CNC Drilling.

The paper presents the effect of nitrogen ion implantation on the tool life of the tools commonly used in the furniture industry for drilling particleboards. Nitrogen ions with different accelerating voltages of 25, 40, 55, and 70 kV and a fluence of 5 × 1017 cm−2 were implanted into the surface of commercially available high-speed steel (HSS) drills, using the implanters without mass-separated ion beams. The tests were carried out in a computerized numerical control (CNC) machining center used in the furniture industry. Based on the measurements of the direct tool wear indicator (W), the drill wear curves were determined and the relative tool life index, standard deviation, coefficient of variation, and the implantation quality index of tool life were calculated. The studies have shown that the modification of the drill surface layer by the nitrogen ion implantation process increases the tool life. The obtained results allow the research to be the continued in a wider scope.

New approach to precisely measure [formula omitted]-ray intensities for long-lived fission products, with results for the decay of 95Zr

For many fission products, the γ rays emitted following β decay provide an easily-detectable signature that can be used to identify their quantities and distributions in a sample. As a result, γ-ray spectroscopy is often exploited to study fission-product yields, provided sufficiently accurate information on the γ-ray intensity is available. However, in many cases, the uncertainties in the existing nuclear data are large enough that they compromise the precision achievable for modern experiments and applications. To address this need, we have developed a new experimental method that is well suited to precisely measure absolute γ-ray intensities in the β decay of long-lived fission products. The approach involves the production of a radiopure sample by implantation of a mass-separated ion beam from the CAlifornium Rare Isotope Breeder Upgrade (CARIBU) facility on a thin carbon foil. The emitted β-decay radiation is detected with a 4π gas proportional counter and a meticulously efficiency-calibrated high-purity germanium (HPGe) detector. As a first measurement to demonstrate the approach, we studied the absolute γ-ray intensities of the strongest transitions following the β decay of 95Zr and its decay-daughter 95Nb, and determined them to fractional precisions of better than 1–2%. In addition, with a larger sample of activity produced through neutron irradiation of an isotopically-enriched Zr foil, we performed a high-precision measurement of the relative γ-ray intensities following the decay of 95Zr with just the HPGe detector. The sample-production method at CARIBU and the coincidence detection approach demonstrated here can be applied to study fission products with half-lives longer than a day, which includes isotopes important not only for nuclear-energy and national-security applications, but also for medical-isotope research and environmental monitoring.

Effect of nitrogen ion implantation on the life time of WC-Co tools used in particleboard milling

ABSTRACT This work explores an effect of nitrogen ion implantation on the life time of WC-Co tools used in particleboard milling. Nitrogen ions with different energy of 5, 50, and 500 keV and fluence of 1e17 and 5e17 cm−2 were implanted into the surface of commercially available WC-Co composite indexable knives, using the implanters with mass-separated ion beams. Both untreated and modified samples were subjected to microstructural and durability tests. Microstructural tests involved surface observation, determination of the nature of wear and cracks, determination of element depth profiles, and phase changes occurring in the modified area. Durability tests were conducted with the use of a computerized numerical control (CNC) machining center. The tests included determination of wear curves and calculation of quantities such as cutting length, relative tool life index, standard deviation, standard error, coefficient of variation and quality index and wear increases. Additionally, a histogram of the relative durability distribution of samples implanted with N+ was determined. In this study, an attempt was made to relate the durability results with the microstructure of the knives. Tools modified with a nitrogen ion beam of 50 keV showed the best durability results.

Impact of Modular Total Absorption Spectrometer measurements of β decay of fission products on the decay heat and reactor ν[over ¯]_{e} flux calculation.

We report the results of a β-decay study of fission products ^{86}Br, ^{89}Kr, ^{89}Rb, ^{90gs}Rb, ^{90m}Rb, ^{90}Kr, ^{92}Rb, ^{139}Xe, and ^{142}Cs performed with the Modular Total Absorption Spectrometer (MTAS) and on-line mass-separated ion beams. These radioactivities were assessed by the Nuclear Energy Agency as having high priority for decay heat analysis during a nuclear fuel cycle. We observe a substantial increase in β feeding to high excited states in all daughter isotopes in comparison to earlier data. This increases the average γ-ray energy emitted by the decay of fission fragments during the first 10 000s after fission of ^{235}U and ^{239}Pu by approximately 2% and 1%, respectively, improving agreement between results of calculations and direct observations. New MTAS results reduce the reference reactor ν[over ¯]_{e} flux used to analyze reactor ν[over ¯]_{e} interaction with detector matter. The reduction determined by the abinitio method for the four nuclear fuel components, ^{235}U, ^{238}U, ^{239}Pu, and ^{241}Pu, amounts to 0.976, 0.986, 0.983, and 0.984, respectively.

Development of a preclinical 211Rn/211At generator system for targeted alpha therapy research with 211At

IntroductionThe availability of 211At for targeted alpha therapy research can be increased by the 211Rn/211At generator system, whereby 211At is produced by 211Rn electron capture decay. This study demonstrated the feasibility of using generator-produced 211At to label monoclonal antibody (BC8, anti-human CD45) for preclinical use, following isolation from the 207Po contamination also produced by these generators (by 211Rn α-decay). Methods211Rn was produced by 211Fr electron capture decay following mass separated ion beam implantation and chemically isolated in liquid alkane hydrocarbon (dodecane). 211At produced by the resulting 211Rn source was extracted in strong base (2N NaOH) and purified by granular Te columns. BC8-B10 (antibody conjugated with closo-decaborate(2-)) was labeled with generator-produced 211At and purified by PD-10 columns. ResultsAqueous solutions extracted from the generator were found to contain 211At and 207Po, isolated from 211Rn. High radionuclidic purity was obtained for 211At eluted from Te columns, from which BC8-B10 monoclonal antibody was successfully labeled. If not removed, 207Po was found to significantly contaminate the final 211At-BC8-B10 product. High yield efficiencies (decay-corrected, n=3) were achieved for 211At extraction from the generator (86%±7%), Te column purification (70%±10%), and antibody labeling (76%±2%). ConclusionsThe experimental 211Rn/211At generator was shown to be well-suited for preclinical 211At-based research. Advances in knowledgeWe believe that these experiments have furthered the knowledge-base for expanding accessibility to 211At using the 211Rn/211At generator system. Implications for patient careAs established by this work, the 211Rn/211At generator has the capability of facilitating preclinical evaluations of 211At-based therapies.

Sci‐Thur AM: YIS – 01: New technologies for astatine‐211 targeted alpha therapy research

Purpose:The short‐range, densely ionizing α‐particles emitted by 211At (t1/2=7.2h) are well suited for the treatment of diffuse microscopic disease, using cancer targeting biomolecules. 211At availability is limited by the rarity of α‐cyclotrons required for standard production. Image‐based dosimetry is also limited for 211At, which emits low intensity X‐rays. Our goal was to leverage state‐of‐the‐art infrastructure at TRIUMF to produce and evaluate two related isotopes, 211Rn (t1/2=14.6h, 73% decay to 211At) as a generator for 211At, and 209At (t1/2=5.4h, X‐ray/gamma‐ray emitter) as a novel 211At surrogate for preclinical imaging studies.Methods:Produced by spallation of uranium with 480 MeV protons, mass separated ion beams of short‐lived francium isotopes were implanted into NaCl targets where 211Rn or 209At were produced by radioactive decay, in situ. 211Rn was transferred to dodecane from which 211At was efficiently extracted and evaluated for clinical applicability. High energy SPECT/CT was evaluated for measuring 209At activity distributions in mice and phantoms.Results:Our small scale 211Rn/211At generator system provided high purity 211At samples. The methods are immediately scalable to the level of radioactivity required for in vivo experiments with 211At. 209At‐based high energy SPECT imaging was determined suitable for pursuing image‐based dosimetry in mouse tumour models. In the future, we will utilize quantitative 209At‐SPECT for image‐based dose calculations.Conclusion:These early studies provided a foundation for future endeavours with 211At‐based α‐therapy. Canada is now significantly closer to clinical targeted α‐therapy of cancer.

Vacuum Chromatography of Tl on SiO2 at the Single-Atom Level

An isothermal vacuum chromatography setup for superheavy element chemistry studies was developed and tested online at the one-atom-at-a-time level. As a model system, the adsorption behavior of thallium on quartz was chosen with respect to a future chemical characterization of its superheavy homologue, element 113 (E113, Z = 113), using the described setup. Short-lived 184Tl (t1/2 = 10.1(5) s) was produced in the reaction 152Gd(35Cl, 3n)184Tl and delivered as a mass-separated ion beam to the chemistry experiment: A subsurface implantation and a subsequent fast thermal release from a metal matrix was followed by isothermal vacuum chromatography as the chemical separation stage. Single atomic species passing this chromatographic separation were finally identified by time- and energy-resolved event-by-event α-spectroscopy using a diamond-based solid-state detector. The derived adsorption enthalpy of −ΔHadsSiO2(Tl) = 158 ± 3 kJ·mol–1 significantly exceeds available data but correlates well with the adsorption...

Offline trapping of 221Fr in a magneto-optical trap from implantation of an 225Ac ion beam

We demonstrate a new technique to prepare an offline source of francium for trapping in a magneto-optical trap. Implanting a radioactive beam of 225Ac, t1/2 = 9.920(3) days, in a foil, allows use of the decay products, i.e. 221Fr, t1/2 = 288.0(4) s. 221Fr is ejected from the foil by the α decay of 225Ac. This technique is compatible with the online accumulation of a laser-cooled atomic francium sample for a series of planned parity non-conservation measurements at TRIUMF. We obtain a 34 % release efficiency for 221Fr from the recoil source based on particle detector measurements. We find that laser cooling operation with the source is 8+10-5 times less efficient than from a mass-separated ion beam of 221Fr in the current geometry. While the flux of this source is two to three orders of magnitude lower than typical francium beams from ISOL facilities, the source provides a longer-term supply of francium for offline studies.

Tribological properties of nanostructured DLC coatings deposited by C60 ion beam

The frictional and wear characteristics of nanostructured DLC films were investigated. The coatings were deposited on silicon substrates by irradiation of a mass-separated C60 ion beam with 5keV of energy and a deposition temperature ranging from 100 to 450°C. The effects of deposition temperature on the surface morphology, nano-structure, mechanical properties and tribological characteristics of the coatings were assessed. Results showed that deposition temperature strongly affects the nanostructure and surface morphology of the coatings. Coatings deposited at temperatures exceeding 350–400°C exhibited an increase in surface roughness as well as compressive stress due to the formation of graphite, which led to a significant increase in the friction coefficient and wear rate. Coatings deposited at 300°C showed the best tribological properties.

Hydrogen isotope exchange in tungsten: Discussion as removal method for tritium

Hydrogen isotope exchange in re-crystallized polycrystalline tungsten was investigated at 320 and 450K. In a first step the tungsten samples were loaded with deuterium to a fluence of 1024D/m2 from a low-temperature plasma at 200eV/D particle energy. In a second step, H was implanted at the same particle energy and similar target temperature with a mass-separated ion beam at different ion fluences ranging from 2×1020 to 7.5×1023H/m2. The analytic methods used were nuclear reaction analysis with D(3He,p)α reaction and elastic recoil detection analysis with 4He. In order to determine the D concentration at depths of up to 7.4μm the 3He energy was varied from 0.5 to 4.5MeV. It was found that already at an H fluence of 2×1020H/m2, i.e. at 1/5000 of the initial D fluence, about 30% of the retained D was released. Depth profiling of D without and with subsequent H implantation shows strong replacement close to the surface at 320K, but extending to all analyzable depths at 450K especially at high fluences, leading to higher release efficiency. The reverse sequence of hydrogen isotopes allowed the analysis of the replacing isotope and showed that the release of D is balanced by the uptake of H. It also shows that hydrogen does not diffuse through a region of filled traps into a region were unfilled traps can be encounter but transport is rather a dynamic process of trapping and de-trapping even at 320K. Initial D retention in H loaded W is an order of magnitude higher than in pristine W, indicating that every H-containing trap is a potential trap for D. In consequence, hydrogen isotope exchange is not a viable method to significantly enhance the operation time before the tritium inventory limit is reached but should be considered an option to reduce the tritium inventory in ITER before major interventions at the end of an operation period.

Ion-induced deuterium retention in tungsten coatings on carbon substrate

Deuterium retention in different tungsten (W) coatings on carbon substrates was investigated for various incident ion energies ranging from 20 to 200 eV per deuterium atom and fluences ranging from 1 × 10 23 m −2 to 2 × 10 25 m −2. The targets were irradiated by deuterium ions at the IPP laboratory with a mass-separated ion beam with a flux of 10 19 D/m 2 s and with a deuterium plasma providing a flux of 10 20 D/m 2 s. Irradiation has been done at different sample temperatures ranging from 320 to 650 K. The depth profile of deuterium in the W coatings was measured up to 6 μm depth by nuclear reaction analysis (NRA) and the total retained amount was determined by thermal desorption spectroscopy. It is shown that deuterium retention significantly depends on the microstructure of each W coating. The deuterium retention in W coating of 7 μm thickness produced by combined magnetron-sputtering and ion implantation technique is higher compared to physical vapour deposited W coating of 4–5 μm thickness and 200 μm thickness plasma-sprayed W coating for all investigated energies and sample temperatures up to 650 K.

Chemical bond analysis of amorphous carbon films

Hydrogen-free carbon films with the various sp 3 bond fractions between 83% and 40% were prepared by mass-separated ion beam deposition (MSIBD). These sp 3 bond fractions were obtained by electron energy loss spectroscopy (EELS). Chemical bond analysis of these carbon films was performed by x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and Raman spectroscopy, and the comparison of these methods was examined. XPS C1s spectra of carbon films show two contributions at the energies of 284.5 and 285.5 eV, which are originated from sp 2-bonds and sp 3 bonds, respectively. The sp 3 bond fractions obtained by XPS are in good agreement with the values given by EELS. The fine structure of AES spectra at the kinetic energy region between 245 and 265 eV reflects the sp 3 bond fraction. AES spectra are changed from the diamond-like feature to the graphite-like one with decreasing the sp 3 bond fraction. Raman spectra show two broad peaks of G band and D band, the ratio of two peak intensities is independent on the sp 3 bond fraction of films. The shift of G peak position has a correlation with the sp 3 bond fraction in the sp 3 bond rich region.

Development of the RF-IGISOL at CYRIC

An rf ion guide for mass separation of fission fragments has been developed as a new type of the ion-source of an ion guide isotope separator on-line (IGISOL). Fission fragments from an uranium target are thermalized in a large helium gas cell and extracted by a combination of dc and inhomogeneous rf electric fields. They are subsequently mass separated by an electromagnetic mass separator. Test experiments with a radioactive α-source and with fission fragments produced in the proton-induced fission of 238U reveal that the yields of mass-separated radioactive ion beams are enhanced, due to the dc and rf electric fields in the gas cell.

Characterization of Ion Beam Deposited 107Ag Thin Films on Si(111) Surface by means of Rutherford Backscattering Spectroscopy and Reflection High Energy Electron Diffraction

The crystalline quality of the 107Ag films on Si(111) surface grown by mass-separated low energy ion beam deposition (IBD) has been studied by means of combined techniques of reflection high energy electron diffraction (RHEED), low energy electron diffraction, and Rutherford backscattering spectroscopy (RBS). Although crystalline quality of the films hardly depends on Ag ion energy in the range of 30-100 eV for RHEED patterns, the RBS-channeling spectra clearly show the difference in the minimum channeling yield Xmin and the increasing rate of the channeling yield dx(z)/dz. The Ag ion energy to obtain a well-crystallized Ag film is found to be 30-50 eV. In addition, it is shown that excellent quality of the Ag films grown at elevated temperature can be obtained by means of IBD.

Characterization of Ion Beam Deposited 107Ag Thin Films on Si(111) Surface by means of Rutherford Backscattering Spectroscopy and Reflection High Energy Electron Diffraction

The crystalline quality of the 107Ag films on Si(111) surface grown by mass-separated low energy ion beam deposition (IBD) has been studied by means of combined techniques of reflection high energy electron diffraction (RHEED), low energy electron diffraction, and Rutherford backscattering spectroscopy (RBS). Although crystalline quality of the films hardly depends on Ag ion energy in the range of 30-100 eV for RHEED patterns, the RBS-channeling spectra clearly show the difference in the minimum channeling yield Xmin and the increasing rate of the channeling yield dx(z)/dz. The Ag ion energy to obtain a well-crystallized Ag film is found to be 30-50 eV. In addition, it is shown that excellent quality of the Ag films grown at elevated temperature can be obtained by means of IBD.

フリーマン型イオン源におけるメチルシランのフラグメントイオンとタングステンワイヤ表面状態

Ion fragmentation of methylsilane by a hot tungsten wire in a Freeman-type ion source was investigated with low-energy mass separated ion beam apparatus for the study of catalytic chemical vapor deposition (Cat-CVD) processes. The mass analysis showed that dominant fragment ions were typically H1+, H2+, H3+, CH3+, SiH+, and SiCH4+. The ion production rates, which depended strongly on the tungsten wire temperature, decreased with time due to modification of the tungsten wire surface during the process. The x-ray diffraction and x-ray photoelectron spectroscopic measurements showed that silicon carbide, carbon, and tungsten carbide compounds were formed on the tungsten wire surface during the process.

低エネルギー質量分離イオンビーム照射装置を用いた金の堆積率の測定

Au deposition rates were measured as a function of Au ion injection energy with the use of a low-energy mass separated ion beam deposition apparatus. Unlike similar measurements reported earlier, in the present experiments, the quality of ion beams (i.e., their mass and energy spectra) was also examined. In the deposition experiments, the Au ion beam was injected into a gold-coated quartz crystal microbalance (QCM), which measures the mass of deposited Au atoms for the given ion beam current. The measured deposition rates in the energy range of 40-200 eV are consistent with those reported in earlier works.

Cubic boron nitride thin film growth by boron and nitrogen ion implantation

Cubic boron nitride $(c\text{\ensuremath{-}}\mathrm{B}\mathrm{N})$ thin films were deposited on silicon substrates using mass separated ion beam deposition (MSIBD). In order to investigate the influence of the ion energy on the growth of $c\text{\ensuremath{-}}\mathrm{B}\mathrm{N}$ films, $^{11}\mathrm{B}^{+}$ and $^{14}\mathrm{N}^{+}$ ions were implanted into $c\text{\ensuremath{-}}\mathrm{B}\mathrm{N}$ with ion energies ranging from $5\phantom{\rule{0.3em}{0ex}}\mathrm{keV}\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}43\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$ and substrate temperatures $({T}_{S})$ from room temperature (RT) to $250\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$. A systematic study on the interplay of ${E}_{\mathit{\text{ion}}}$ and ${T}_{S}$ has revealed a characteristic energy-dependent temperature threshold for $c\text{\ensuremath{-}}\mathrm{B}\mathrm{N}$ growth. This behavior is explained by dynamic annealing of defects caused by a penetrating ion in a collison cascade. In this picture, the suppression of defect accumulation that is crucial for maintaining cubic phase formation is attributed to temperature-driven back diffusion and subsequent annihilation of B and N interstitial recoils. The model is confirmed by analyzing the depth profile of implanted, isotopically pure $^{10}\mathrm{B}$, and its application for both $c\text{\ensuremath{-}}\mathrm{B}\mathrm{N}$ nucleation and growth is discussed.